Molecular Structure of Histamine phosphate (CAS NO.51-74-1):

Molecular Formula C₅H₉N₃.2(H₃PO₄)
Molecular Weight 307.13
IUPAC Name: 2-(1H-Imidazol-5-yl)ethanamine; phosphoric acid 
Synonyms of Histamine phosphate (CAS NO.51-74-1): Histamine phosphate [USP] ; 4-(2-Aminoethyl)imidazole bis(dihydrogen phosphate) ;  4-(2-Aminoethyl)imidazole di-acid phosphate ; EINECS 200-118-4 ; Histamine acid phosphate ; Histamine biphosphate ; Histamine dihydrogen phosphate ; Histamine diphosphate ; Histamine phosphate (1:2) ; Histamine positive ; UNII-QWB37T4WZZ ; 1H-Imidazole-4-ethanamine, phosphate (1:2) ; 2-Imidazol-4-ylethylamine orthophosphoric acid (1:2)
CAS NO: 51-74-1
Classification Code: Histamine Agents ; Neurotransmitter Agents ; Reproductive Effect ; Stimulant [gastric secretory] Stimulant [gastric secretory]
Flash Point: 180.3 °C
Enthalpy of Vaporization: 57.36 kJ/mol
Boiling Point: 331 °C at 760 mmHg
Vapour Pressure: 0.00016 mmHg at 25°C
nChI
InChI=1/C5H9N3.2H3O4P/c6-2-1-5-3-7-4-8-5;2*1-5(2,3)4/h3-4H,1-2,6H2,(H,7,8);2*(H3,1,2,3,4)
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Smiles
[nH]1cnc(CCN)c1.P(O)(=O)(O)O.P(O)(=O)(O)O
Classification Code: Histamine Agents; Neurotransmitter Agents; Reproductive Effect; Stimulant

 Histamine phosphate (CAS NO.51-74-1) has been used for the presumptive diagnosis of pheochromocytoma; however, the use of histamine in patients suspected of having pheochromocytoma is hazardous and unwarranted due to the risk of precipitating a hypertensive crisis. Histamine phosphate has been used to produce short-term improvement in patients with vertigo, tinnitus, and deafness. However, it has not been proven effective in the symptomatic treatment of Menière's disease.

Reported in EPA TSCA Inventory.

A deadly poison by intravenous and parenteral routes. Moderately toxic by ingestion and intraperitoneal routes. When heated to decomposition it emits very toxic fumes of NO_x and PO_x.